<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    // 示例1 变量
    var num = 123;
    alert(num.toString());//"123"
    var boo = false;
    alert(num.toString());//"false"
</script>
</html>
